Vehicle door latch assemblies frequently incorporate a door handle assembly with a release handle that is pulled away from the door in order to operate the latch mechanism and open the door. In the case of an impact event such as a collision, particularly one that generates an impact force vector perpendicular to the side of the vehicle, the acceleration of the vehicle in the direction of the side-acting force vector can cause the release handle to pull away from the door, thereby inadvertently actuating the latch mechanism.
As shown in the graph of FIG. 1, impact events such as those described above are characterized by a positive acceleration phase 1 preceded by an initial negative acceleration phase 2 of about 5 msec in duration. The positive acceleration phase corresponds to a period of time when the impact force is directed inwardly toward the door, while the negative acceleration phase corresponds to a preceding period of time, immediately following the impact event, when the impact force is initially translated to a net vector directed outwardly away from the door; i.e., a negative acceleration.
In order to minimize the potential for unintended, impact-induced door opening, vehicle-door release-handle suppliers have developed inertial blocking member subassemblies that impede the unintended movement of the release handle assembly and/or door opening actuator resulting from an impact to the vehicle. These subassemblies are activated between an at-rest position, wherein the door, if functional, can be opened by operating the release handle, and a blocking position, wherein opening of the door is prevented by impact-generated forces. Impeding the movement of the release handle assembly or door opening actuator can thus be accomplished by controlling impact-based acceleration and inertial effects associated with the inertial blocking member subassembly.
Known inertial blocking member subassemblies are configured, generally with a biasing element, to return to the at-rest position, thus enabling the door to be opened in the usual manner in after an impact event.
However, known inertial blocking member subassemblies are only effective during the positive acceleration phase. This is due to the fact that the principle of operation of most conventional inertial blocking member subassemblies is based upon a freely-rotating mass defining an offset (relative to an axis of rotation of the inertial blocking member between the at-rest and blocking positions) center of gravity, which mass is moved by the positive acceleration force of an impact event to carry the blocking member from the at-rest position to the blocking, or engaged, position. Consequently, there exists the potential for conventional inertial blocking subassemblies to fail to respond rapidly enough to the onset of the positive acceleration phase to prevent the release handle from pulling away from the door and inadvertently actuating the latch mechanism.